Topological Structure Design Of Low-orbit Satellite Constellation

With the continuous advancement of the integration of space and ground,the low orbit satellite networks have been widely used in real-time communication,finance and other fields because of their wide coverage and low latency.Therefore,countries are actively constructing large-scale low-orbit satellite networks,such as Starlink.At present,most of the research results are mainly concentrated in the field of routing design of low-orbit satellites,while ignoring the influence of topology on the efficiency of inter-satellite networking and the quality of inter-satellite communication.In addition,due to the large number of satellites in large LEO satellite networks,the existing intersatellite topology construction methods are not applicable.Therefore,on the basis of analyzing the existing topology construction methods and using the periodic law of satellite operation,this paper designs the intersatellite topology.The specific work of this paper is as follows:First,in order to take into account different communication requirements,this paper proposes Static Topology of LEO Satellites(STLS).The key to construct STLS lies in satellite constellation analysis,link evaluation and chain building strategy.Firstly,this paper uses STK simulation tools to solve the optimal phase factor,analyzes the inter-satellite visibility and the trend of link azimuth,elevation and distance with time;Secondly,according to different communication requirements,a link evaluation function is proposed considering the distance between satellites and the visual time of connection;Finally,each satellite is assigned two fixed links in the same orbit and two fixed links between adjacent orbits,and the law that the nearest satellite in adjacent orbit remains unchanged at any time is obtained.The simulation results show that STLS improves communication performance,avoids the link switching,and reduces the delay effectively.Second,this paper analyzes the limitations of STLS and proposes Dynamic Topology of LEO Satellites(DTLS).DTLS allocates three fixed links and one dynamic link for each satellite,making the topology more flexible and reliable.The key to constructing DTLS lies in the selection of fixed links,the division of time slices,and the establishment of dynamic links.The fixed links are selected based on STLS,and there are two combinations to ensure the connectivity between satellites;The number of time slices is the same as the number of satellites per orbit,which ensures the correlation between dynamic links in different time slices;The dynamic link connects the non-adjacent orbit satellites which have shorter distance than the adjacent orbit links and follow the law.The simulation results show that DTLS can greatly reduce the communication delay and information forwarding hops,thus improving the network performance.Third,in order to improve the stability of DTLS,this paper analyzes the situation of satellite failure,and proposes three reconstruction strategies for the affected satellites.Furthermore,the Dynamic Topology Reconstruction Algorithm(DTRA)is designed based on the maximum connectivity and the relative minimum link delay.According to DTRA,the strategy with the relatively shortest distance can be derived from the three strategies.The simulation results show that DTRA significantly reduces the time delay.In summary,in order to solve the problem of topology construction and reconstruction of large-scale low-orbit satellite networks,this paper first proposed STLS;secondly,DTLS is designed on the basis of STLS;then,considering the stability of the topology,DTRA is proposed;finally,simulation experiments verify the effectiveness of the algorithm and the superiority of the topology.